Experimental Study on the Effect of the Ignition Location on Vented Deflagration of Hydrogen-air Mixtures in Enclosure

No countermeasures exist for accidents that might occur in hydrogen-based facilities (leaks, fires, explosions, etc.). In South Korea, discussions are underway regarding measures to ensure safety from such accidents, such as the construction of underground hydrogen storage tank facilities. However, explosion vents with a minimum ventilation area are required in such facilities to minimize damage to buildings and other structures due to accidental explosions. These explosion vents allow the generated overpressure and flames to be safely dispersed outside; however, a safe separation distance must be secured to minimize damage to humans. This study aimed to determine the safe separation distance to minimize human damage after analyzing the dispersed overpressure and flame behavior following a vent explosion. Explosion experiments were conducted to investigate the influence of the ignition source location on internal and external overpressure and external flame behavior using a cuboid concrete structure with a volume of 20.33 m3 filled with a hydrogen-air mixture (29.0 vol.%). The impact on overpressure and flame was increased with the increasing distance of the ignition source from the vent. Importantly, depending on the ignition location the incident pressure was up to 24.4 times higher, while the reflected pressure was 8.7 times higher. Additionally, a maximum external overpressure of 30.01 kPa was measured at a distance of 2.4 m from the vent, predicting damage to humans at the “Injury” level (1 % fatality probability). Whereas, no significant damage would occur at a distance of 7.4 m or more from the vent.